It could be anywhere on any radial from where the last ping occurred to where the next ping would have occurred. That's potentially a long distance.
That would require another hour of fuel. The time where the next ping would have occurred is irrelevant, only the fact that it did not occur, and that the last handshake was initiated from the airplane and was incomplete.
We don't even know if the satellites data is reliable.
I don't see any reason to doubt the reliability of the Inmarsat logs. The real question is how accurate the BFO and BTO values are. The notes that precede the logs in the Inmarsat release discuss the sources of several inaccuracies.